Using DEM to assess the influence of stress and fabric inhomogeneity and anisotropy on susceptibility to suffusion

Underfilled and gap-graded soils are known to be susceptible to suffusion; a form of internal instability in which the finer fraction of a soil is washed out from the coarser matrix under the action of seepage. This phenomenon poses a risk to embankment dams and flood embankments. The processes and mechanisms operate at the particle scale, and insight can be gained via the particulate discrete element method (DEM). Vir-tual samples can be created using DEM and simulation results can provide information on particle stresses, as well as quantitative information on the fabric of the particulate material. This is important as the amount of stress carried by the finer particles is thought to govern the susceptibility of a given material to suffusion. DEM modelling can also provide information on variation in properties within samples as well as the detailed data needed to quantify the material fabric. DEM models are, however, an idealization of reality and con-strained in particular by the number of particles used and sample preparation method. This study examines key issues relating to the development of virtual samples for use in DEM analysis and also examines the proportion of the applied stress that is carried by the finer particles.